1. Field of the invention
The resent invention relates to an Albada type inverted Galilean finder for a photographic camera and, more particularly, to an Albada type inverted Galilean finder which includes a frame projection optical system.
2. Description of Related Art
Modern compact cameras, widely used for nonprofessional purpose, are typically equipped with various automatic features, such as automatic exposure, automatic focusing, automatic film winding, low luminance flash exposure, etc. Such an automatic compact camera provides various opportunity of taking pictures with ease for amateur photographers. These automatic compact cameras of the middle class are typically equipped with Albada type inverted Galilean finders.
The Albada type Galilean finder typically has a finder lens system including an objective lens element, an eyepiece element formed with framing markings on one surface facing the objective lens element, and a half mirror disposed between the objective lens element and the eyepiece element for projecting the framing markings. Increasing of the magnification of the finder lens system renders the finder increased in its overall length and is undesirable for minimized or downsized photographic cameras. For this reason, most compact cameras are typically equipped with finders whose finder lens systems have magnifications of 0.4 to 0.5.
One of recent strong demands on compact cameras is, in addition to be easy-to-view, to be small, thin and lightweight and to be manufactured at low cost. In an attempt to minimize Albada type inverted Galilean finders and provide them with clear view, it has been the main stream to constitute finder lens systems having two lens elements and provide large magnifications for the finder lens systems. Such a finder lens system makes it difficult to incorporate the finder in a camera with remaining the camera remained small and thin. Further, a large magnification of the finder lens system needs to use thick lens elements, hindering providing a lightweight camera.